Keep surfaces disinfected: coronavirus survives longer on glass, plastic than on fabric and paper

NEW DELHI: The novel coronavirus can survive much shorter time on porous surfaces such as paper and clothing than on impervious surfaces like glass and plastic, suggests a study by researchers at the Indian Institute of Technology (IIT ) from Bombay.

COVID-19, caused by the SARS-CoV-2 virus, is transmitted by respiratory droplets. The virus-laden droplets also form fomite when falling on a surface, which serves as a source of spread of infection.

In the study, published in the journal Physics of Fluids, the researchers analyzed the drying of droplets on impermeable and porous surfaces.

They found that a droplet remains liquid for a much shorter time on a porous surface, which makes it less favorable for the virus to survive.

Research suggests the virus can survive for four days on glass and seven days on plastic and stainless steel.

However, the virus only survived three hours and two days on paper and tissue, respectively, the researchers said.

“Based on our study, we recommend that hospital and office furniture, made of waterproof materials, such as glass, stainless steel or laminated wood, be covered with a porous material, such as fabric, to reduce the risk of infection by touching, ”said study author Sanghamitro Chatterjee from IIT Bombay.

The study also suggests that seats in public places, such as parks, shopping malls, restaurants and waiting rooms at railways or airports, could be covered with fabric to reduce the risk of the spread of disease.

According to the researchers, 99.9% of the liquid content of the droplet for impermeable and porous surfaces evaporates within the first few minutes.

They noted that after this initial state, a microscopic residual thin liquid film remains on the exposed solid parts, where the virus can still survive.

The team, including Janani Srree Murallidharan, Amit Agrawal and Rajneesh Bhardwaj, also from IIT Bombay, found that the evaporation of this residual thin film is much faster in the case of porous surfaces than in impermeable surfaces.

The droplets propagate due to capillary action between liquid near the nip and horizontally oriented fibers on the porous surface and void spaces in porous materials, which accelerates evaporation, the researchers said.

“The fact that only the geometric characteristics rather than the chemical details of the porous material significantly reduce the life of thin films,” Bhardwaj explained.

The researchers said the study results, such as the droplet’s liquid-phase lifespan of around six hours on paper, will be particularly relevant in certain settings, such as schools.

While this time frame is shorter than that of any permeable material, such as glass with a liquid phase life of around four days, it would impact the laptop swap, they said.

For example, the researchers said, it could be useful when policymakers are evaluating safe measures for reopening schools or exchanging banknote transactions at retail banks.

Likewise, they said cardboard boxes, commonly used by e-commerce companies around the world, could be considered relatively safe, as they would inhibit the survival of the virus.